Type 1 Diabetes Mellitus (T1DM) is an increasingly prevalent form of diabetes in which the insulin-producing ?- cells of the pancreas are destroyed by an autoimmune attack, and as a result, no endogenous insulin is produced. Most often diagnosed in children, 1-3 million Americans suffer from T1DM, and ~80,000 new cases are diagnosed annually worldwide. T1DM profoundly impacts patients? health and quality of life due to the constant need to measure blood glucose levels, to normalize those levels with insulin injections, and to strictly adhere to special dietary requirements. Even with these methods, many diabetics achieve only erratic or limited control over their blood glucose levels. As a result, fluctuations in blood glucose levels occur, leading to complications such as end-stage renal failure, blindness, and non-traumatic amputations. Given the quality of life and health consequences suffered by millions of T1DM patients, new and effective treatments remain an urgent, unmet need. Endsulin, Inc, (Madison, WI) proposes to develop a treatment for T1DM based on an insulin expression transgene therapy that is expected to result in glucose-dependent insulin secretion from the liver of T1DM patients. The treatment will be noninvasive, requiring a single intravenous injection, and should control blood glucose levels in patients with T1DM while preventing or minimizing secondary diabetic complications. Preliminary studies conducted at the University of Wisconsin-Madison and the University of Pennsylvania have shown that a novel gene therapy construct consisting of a destabilized human insulin mRNA expressed under the control of a glucose-responsive promoter can restore glycemic control in a rodent model of T1DM without inducing post-prandial hypoglycemia, which has been a limitation of earlier attempts at the use of insulin gene therapy constructs. In this Phase I STTR, Endsulin will work cooperatively with the University of Wisconsin to demonstrate the feasibility of this gene therapy approach. In Aim 1, the therapeutic dose of the gene therapy construct, delivered using adeno-associated virus, will be optimized in streptozotocin-treated mice, a well-accepted model of T1DM. In Aim 2, the therapeutic dose will be optimized in experimental diabetic dogs, and the long-term safety and efficacy of the therapy will be determined. In the planned Phase II studies, Endsulin intends to conduct long-term (2-3 year) preclinical studies on spontaneously diabetic companion dogs, to be followed with FDA - IND approval and human trials. With this innovation, T1DM patients may no longer need to test their blood glucose levels or inject themselves with insulin multiple times each day. Aside from the enormous health and lifestyle benefits, the T1DM gene therapy approach developed here should dramatically reduce the economic costs of this increasingly common condition.